function tf = is_vbasis(V)
%IS_VBASIS Tests whether the input is a vector field basis
%
%   tf = IS_VBASIS(V);
%
%       Returns true is V is a struct representing a vector field basis.
%

% Created by Dahua Lin, on April 4, 2012

%% main

tf = isstruct(V) && numel(V) == 1 && isfield(V, 'tag') && ...
    isequal(V.tag, 'vbasis');